It is known that logs consisting of a predetermined amount of a paper web wound around a tubular cardboard core, which is usually made of cardboard, are used for producing rolls of toilet paper, rolls of kitchen blotting paper or similar rolls. Each log is subdivided into a given number of rolls having shorter lengths by means of a cutting machine. Since the two ends of the logs are normally orthogonal to the longitudinal axis of the cardboard core and the cardboard core may jut out of one or of both ends of the paper logs, for each log the cutting machine cuts first a reduced portion of the front end, and then it cuts pieces which correspond to rolls having the desired length. The last cut is performed on a reduced portion of the tail end of the log. The front and the tail end portions of the logs so produced, usually called trims, are to be discarded to avoid their packaging together with the rolls destined for sale.
Suitable devices, positioned between the exit of the cutting machine and the entrance of the packaging line, are used for this purpose and provide for the discarding of the trims.
EP0995559 discloses a device for transferring rolls, which have been obtained by cutting a log, from a first to a second conveyor, provided with a mechanism for moving away the trims which are present at the beginning and at the end of each succession of rolls. The mechanism comprises two shuttles mounted on a framework associated with the first and the second conveyor and which are so shaped that they provide a sliding plane for the rolls or an empty space between the first and the second conveyor depending on their reciprocal position. More precisely, whenever it is necessary to produce an empty space between the first and the second conveyor, the two shuttles are distanced from each other, so the trims coming from the first conveyor fall downward under the effect of gravity. In this way, it is possible to avoid the transfer of the trims from the first to the second conveyor.
EP 1281487 discloses a device for eliminating trims from a succession of rolls coming from a cutting machine. The device is disposed and acts downstream of a feeding unit for the rolls and trims coming from the cutting machine and it consists of a ring-closed conveyor. The conveyor is provided with an opening the size of which allows the trims to fall through it. The opening is disposed at the end point of the feeding unit by suitably handling the conveyor, whenever the head and tail trims of the succession of rolls reach a given point.
US44 622287 discloses a mechanism for eliminating or discarding trims from a succession of rolls obtained by subdividing a log which, unlike the cases mentioned above, does not imply a system positioned and acting between the feeding units upstream and the collecting units downstream, provides for the use of a device for modifying the shape of the collecting unit downstream. More particularly, the conveyor which transports the rolls coming from the cutting machine has a variable length, as it can assume an elongated position in which it is close to the conveyor upstream or a retracted position in which it is distanced from the conveyor. Thus, when the rolls are transferred, the second conveyor is elongated so as to provide a basically continuous transferring surface between the first and the second conveyor. On the contrary, in order to avoid transferring a trim from the first to the second conveyor, the second conveyor is retracted so as to produce an empty space into which the trim may fall under gravity.
A similar device is described in US6607082 which relates to a device for eliminating or discarding trims which provides for the modification of the shape of the conveyor destined to move the rolls away from the cutting machine.
US2003/0167887 describes a device for eliminating or discarding trims which is somehow hybrid with respect to those described above, as it provides for the use of belts having a variable conformation disposed and acting between a unit for moving away the rolls and the trims produced and the trims produced by a cutting machine and a unit for collecting the single rolls.
EP0982106 discloses a device for eliminating or discarding trims which provides for subdividing into two sections the conveyor for collecting the single rolls: the section which is closer to the belts for moving the rolls and the trims away from the cutting machine can be rotated so that it can be lifted to avoid the passage of trims to the second section or it can be lowered and put in a horizontal position so as to form a bridge for transferring the single rolls which, in this way, pass from the cutting machine to the second section.